Substituted disulfides as antifoggants for silver halide emulsions



July 10, 1962 A. H. HERZ ETAL 3,043,696

SUBSTITUTED DISULFIDES AS ANTIFOGGANTS FOR SILVER HALIDE EMULSIONS FiledSept. 4, 1959 L0 I: 8 2 6 g l l l O 263' 7.53 0 0.43

LO (5 E .ArlhurILHerZ NormanWKalenda INVENTORS' gfiai /w i ATTORNEY;

United States Patent "ice 3,043,696 SUBSTITUTED DISULFIDES ASANTIFOGGANTS FOR SILVER HALIDE EMULSIONS Arthur H. Herz and Norman W.Kalenda, Rochester,

N.Y., amignors to Eastman Kodak Company, Rochester, N.Y., a corporationof New Jersey Filed Sept. 4, 1959, Ser. No. 838,224 11 Claims. (Cl.96-108) This invention relates to the stabilization of photo graphicsilver halide emulsions, and. more particularly,

to a method of inhibiting development of spontaneous fog withoutadversely affecting the sensitivity of the photographic silver halideemulsions.

It is well known that photographic emulsions on storage tend to losesensitivity and to become spontaneously developa-blewithout exposure tolight. There is normally a detectable amount of the silver salt reducedduring development in the areas where no exposure was given; this iscommonly called fog, and sometimes called chemical fog Where it isnecessary to distinguish between it and the eiiects of accidentalexposure to radiation; in this in-. vention, we are not concerned withthe latter.

Fog depends both on the emulsion and the conditions of development; fora given emulsion it increases with the degree of development. Withconstant development con ditions, it tends to increase with time,temperature and relative humidity of storage conditions; it is commonpractice to make accelerated tests of the stability of photographicemulsions by storage at increased temperature or humidity, or both. Itis, of course, desirable to have emulsions as stable as possible underthe conditions of high temperature and humidity which may occur intropical climates, for example. Fog usually appears over the whole areaof the sensitive coating, but when severe, it frequently is non-uniform..Fog may also be caused by exposure to chemicals, for example, hydrogensulfide and 3,043,696 Patented July 10, 1962 duction into the emulsion,for example, by bathing, im-' practical.

It is, therefore, an object of our invention to provide. a method ofstabilizing photographic silver halide emulsions. Another object is toprovide a method of stabilizing photographic silver halide emulsionswithout afiecting to any material extent the sensitivity of theemulsions. Another object is to provide a method of stabilizing bothunsensitized and sensitized emulsions, without introducing anysubstantial sensitizing or desensitizing elfect. Still another object isto provide new organic disulfides and a method of preparation. Otherobjects will become apparent from a consideration of the followingdescription and examples. According to our invention, photographicsilver halide emulsions can be stabilized and the development 0tspontaneous fog substantially inhibited by incorporating therein certainorganic disulfides. P The advantages of our invention, as compared withthe prior art, are illustrated in FIGURE 1 of the accompanying drawing.a

The substituted organic disulfides useful in practicing our inventioncan be represented by the following general formula:

COOR! COORi fonyl, toluenesulfonyl, etc. (i.e., an acyl group of anali-' other reactive sulfur compounds, hydrogen peroxide vapor, andstrongly reducing materials. While antifog-j gants and stabilizers mayprotect, to some extent, against such efiects, it is normally understoodthat antifoggants protect against spontaneous growthof fog duringprolonged storage or storage at high temperatures and humidities, orduring development to maximum contrast and. speed, or both.

In emulsion technology, the use of certain organic disulfides aschemical sensitizers and stabilizers against in cubation fog has beenpreviously described. Unfortunately, many of these disulfides haveproperties which place them in more than one of the above categories.For example, cystine is known to exhibit both sensitizing and example:

antifoggant behaviour. In like manner, the disulfides obtained fromcertain mercapto carboxylic acids, such as those described in Matthieset al., US. Patent 1,742,042, issued December 31,1929, have primarily asensitizing efiect on photographic silver halide emulsions, with a muchless marked effect upon the stability of the emulsions,

Because of the above facts, the use of such organic disulfides asantifoggants, offers practical disadvantages; Such disulfides havingboth sensitizing and some stabilizing activity cannot be employed inunsensitized or undersensitized emulsions. In fully sensitized,high-speed emulsions, the sensitizing or desensitizing disulfides, ifthey are to act as-fog restrajners, must be used at narrow andcontrolled concentration levels, thus making their introphatic oraromatic carboxylic acid, or an acyl group of an aliphatic or aromaticsulfonic acid), R 'represents a hydrogen atom, an alkali metal atom(e.g., sodium,-potassium, etc.), an ammonium group (i.e., ammonium ororganic ammonium, including pyridinium, triethylammonium,triethanolammonium, etc.), or a lower alkyl group, such as methyl,ethyl, etc, and n represents a posi-f tive integer of from about 1 to 4.Typical organic disulfides embraced by Formula 1 above which can be usedin practicing our invention include the following, for

a,a-Di (methanesulfonamido) -'y,'y'-dithiodibutyric acid CsHNHCHOHgCHgOHy-S-S-CHzCHzCHzCHNH-il) 00135 c 0 OH 0 0 OHa,a.'-Dibenzamido-6,6-'dithiodivaleric acid (9) carols-Juno]: o Hes-s4:H2 0 HNHS 020,119

7 C O OH O O OH a,a-Di(butanesulfonamido)-,3,l3-dithiodipropion.ic acidCOOC-tHa COOC4H9 'Butyl a,a '-di(methanesulfonamid o43,8-dithiodipropionate For the purpose of inhibiting fog formation, thedisulfides of; our invention can be added to the emulsion during theprocess of manufacture in order to avoid loss of sensitivity and toinhibit the growth of fog with passage of time 'undernon-idealconditions of storage.

i An aqueous or organic; solution of the disulfides of our invention.when added at suitable concentration to unsensitized,chemically-sensitized, or optically-sensitized photographic emulsionsdoes not appreciably affect the sensitometric values for sensitivity andfog when measurements are made soon after coating. When sensitometricmeasurements are made at appreciable intervals of time, atelevated'tempenatures and dry or somewhat humid conditions, thedisulfides of our invention do stabilize speed and maintain-fog at-a lowlevel. a

The preparation of silver halide emulsions involves three separateoperations: (1) the emulsification and digestion 0r ripening of thesilver halide, (2) the freeing of the emulsion from excess solublesalts, usually by washing, and (3) the second digestion orafter-ripening to obtain increased sensitivity. (Mees, The Theory of thePhotographicProcess (1942), Macmillan Co.) We prefer to add thefog-inhibiting agents after the final digestion or after-ripening,although they can advantageously be added prior to-digestion. v Ifdesired, the disulfides of our invention can be incorporated in theemulsions without adverse effects by bath i'ng techniques known to thoseskilled in the art.

,' The photographic emulsions used in practicing our invention areof thedeveloping-out type.

' i The emulsions" can be chemically sensitized by any of the acceptedprocedures. The emulsions can be digested with naturally active gelatin,or sulfur compounds can 2,448,060, issued August 31, 194 8, and asantifoggants in higher amounts, as described in Trivelli and Smith U.S.Patents 2,566,245, issued August 28, 1951 and 2,566,263, issued August28,1951.

The emulsions can also be chemically sensitized with gold salts asdescribed in Waller et la]. U.S. Patent 2,399,- 083, issued April 23,1946, or stabilized with gold salts as described in Damschroder U.S.Patent 2,597,856, issued May 27, 1952, and Yutzy and Leermakers U.S.Patent 2,597,915, issued May 27, 1952. Suitable compounds are potassiumchloroaurite, potassium'aurithiocyanate, potas- 4 sium chloroaurate,auric trichloride and 2-aurosulfobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agentssuch as stannous salts (Carroll U.S. Patent 2,487,850, issued November15, 1949), polyarnines, such as diethyl triamine (Lowe and Jones U.S.Patent 2,518,- 698, issued August 15, 1950), polyamines, such asspermine (Lowe and Allen U.S. Patent 2,521,925, issued September 12,1950), or bis(B-aminoethyl) sulfide and its water-soluble salts (LoweandJones U.S. Patent 2,521, 926, issued September 12, 1950).

The emulsions can also be optically sensitized with cyanine andmerocyanine dyes, such as those described in Brooker U.S. Patents1,846,301, issued February 23, 1932; 1,846,302, issued February 23,1932; and 1,942,854, issued January 9,. 1934; White U.S. Patent1,990,507, issued February 12, 1935; Brooker and White U.S. Patents2,112,140, issued March 22, 1938; 2,165,338, issued July 11, 1939;2,493,747, issued January 10, 1950 and 2,739,- 964, issued March 27,1956; Brooker and Keyes U.S. Patent 2,493,748, issued January 10, 1950;Sprague U.S. Patents 2,503,776, issued April 11, 1950 and 2,519,001,issued August 1950; Heseltine and Brooker U.S. Patent 2,666,761, issuedJanuary 19, 1954; Heseltine U.S. Patent 2,734,900, issued February 14,1956; Van Lare U.S. Patent 2,739,149, issued March 20, 1956; and KodakLimited British Patent 450,958, accepted July 15, 1936.

The emulsions can also be stabilized with the mercury compounds ofAllen, Byers and Murray U.S. Patent 2,728,663, issued December 27, 1955;Carroll and Murray U.S. Patent 2,728,664, issued December 27, 1955; and

Leubner and Murray U.S. Patent 2,728,665, issued December 27, .1955; thetriazoles of Heimbach and Kelly U.S. Patent 2,444,608, issued July 6,1948; the azaindenes of Heimbach and Kelly U.S. Patents 2,444,605 and2,444,- 606, issued July 6,1948; Heimbach U.S. Patent 2,444,607, issuedJuly 6, 1948 and 2,450,397, issued September 28, 1948; Heimbach andClark U.S. Patent 2,444,609, issued July 6, 1948; Allen and ReynoldsU.S. Patents 2,713,541, issued July 19, 1955, and 2,743,181, issuedApril 24, 1956; Carroll and Beach U.S. Patent 2,716,062,issued August23, 1955; Allen and Beilfuss U.S. Patent 2,735,769, issued February 21,1956; Reynolds and Sagal U.S. Patent 2,756,147, issued July 24, 1956;Allen and Sagura U.S. Patent 2,772,164, issued November 27, 1956, andthose disclosed by Birr in Z. wiss. Phot., vol. 47, 1952, pages 2-28;the disulfides of Kodak Belgian Patent'569,317, issued July 31, 1958;the quaternary benzothiazolium compounds of Brooker and Staud U.S.Patent 2,131,038, issued Septerrrber 27, 1938, or the polymethylenebisbenzothiazoli-um salts of Allen and Wilson U.S. Patent 2,694,716,issued November 16, 1954; (e.g. decamethylene bis-benzothiazoliumperchlorate); or the zinc and cadmium salts of Jones -'U.S. Patent2,839,405, issued June 17, 1958.

I The emulsions may also contain speed-increasing compounds of thequaternary ammonium type of Carroll U.S. Patent 2,271,623, issuedFebruary 3, 1942; Carroll and Allen U.S. Patent 2,288,226, issued June30, 1942; and Carroll and Spence U.S. 'Patent 2,334,864, issued-November 23, 1943; and the polyethylene glycol type of Carroll and BeachU.S. Patent 2,708,162, issued May 10, 1955, as well as the thiopol-ymersof Graham and Sagal U.S. application Serial No. 779,839, filed December12, 1958, and Dann and Chechak U.S. application Serial No. 779,874,filed December 12, 1958.

The emulsions may contain a suitable gelatin plasticizer such asglycerin; a dihydroxy alkane such as 1,5-pentane diol as described inMilton and Murray U.S. application 0 Serial No. 588,951, filed June 4,1956; an ester of an ethylene bis-glycolic acid such as ethylenebis(met1hyl glycolate) 'as described in Milton U.S. application SerialNo. 662,564, filed May 31, 1957; bis-( ethoxy diethylene glycol)succinate as described in Gray U.S. application Serial No. 604,333,filed August 16, 6, or a polymeric hydrosol as results from the emulsionpolymerization of a mixture of an amide of an acid of the acrylic acidseries, an acrylic acid ester and a styrene-type compound as describedin Tong U.S. Patent 2,852,386, issued September 16, 1958. Theplasticizer may be added to the emulsion before or after the addition ofa sensitizing dye, if

used. a

The emulsions may be hardened with any suitable hardener for gelatinsuch as formaldehyde; a halogensubstituted aliphatic acid such asmucobromic acid as described in White U.S. Patent 2,080,019, issued May11, 1937; a compound having a plurality of acid anhydride groups such as7,8-diphenyl-bicyclo (2,2,2)-7-octene- 2,3,5,6-tetra-carboxylicdianhydride, or a dicarboxylic or a disulfonic acid chloride such asterephthaloyl chloride or naphthalene-1,5-disulfonyl chloride asdescribed in Allen and Carroll U.S. Patents 2,725,294, and 2,725,295,both issued November 29, 1955; a cyclic l, 2-diketone such ascyclopentane-1,2-dione as described in Allen and Byers U.S. Patent2,725,305, issued November 29, 1955; a bisester of methane-sulfonic acidsuch as 1,2-di-(methane-sulfonoxy)-ethane as described in Allen andLaakso U.S. Patent 2,726,162, issued December 6, 1955; 1,3-dihydroxy-methylbenzimidazol-Z-one as described in July, Knott andPollak U.S. Patent 2,732,316, issued January 24, 1956; a dialdehyde or asodium bisulfite derivative thereof, the aldehyde groups of which areseparated by 2-3 carbon atoms, such as fl-meth-yl glutaraldehydebissodium bisulfite as described in Allen and Burness U.S. patentapplication Serial No. 556,031, filed December 29, 1955; a bis-aziridinecarb'oxamide such as trimethylene bis(1-aziridine carboxamide) asdescribed in Allen and Webster U.S. patent application Serial No.599,891, filed July 25, 1956; or 2,3-dihydroxy dioxane as described inwith an alcohol or an aliphatic amine containing fromr 8 to 18carbonatoms which is treated with a base, for example, the sodium saltof the monoester of tetracarboxybutane as described in Knox, Stenbergand Wilson U.S. Patent 2,843,487, issued July 15, 1958; a watersolublemaleopimarate or a mixture of a water-soluble maleopimarate and asubstituted glutamate salt as described in Knox and Fowler U.S. Patent2,823,123, issued February 11, 1958; an alkali metal salt of asubstituted amino acid such as disodiunr-N- (carbo-p-tert.octylphenoxypentaethoxy)glutamate as described inf Knox. and Wilson U.S.patent application Serial No. 600,679, filed July 30, 1956; or asulfosu'ccinamate such as tetrasodium N-( 1,2-dicarb oxyethyl)-N-octadecylsulfosuccinamate or N-la'u'ryl disodium sulfosuccinamateasdesoribed in Knox and Stenberg U.S. patent'application Serial No.-

691,125, filed October 211, 1957.

The addenda which we have described may be used in various kinds ofphotographic emulsions. In addition to being useful in X-ray and othernonoptically sensitized emulsions they may also be used inorthochromatic, panchromatic, and infrared sensitive emulsions. They maybe added to the emulsion before or after any sensitizing dyes which areused. Various silver salts may be 1186i as the sensitive salt such assilver bromide, silver iodide, silver chloride, or mixed silver halidessuch as silver chlorobromide or silver bromoiodide. The agents may beused in emulsions intended for color photography, forexample, emulsionscontaining color-forming couplers or emulsions to be developed bysolutions containing couplers or other color-generating materials,emulsions of the mixed-packet type, such as described in Godowsky U.S.Patent 2,698,794, issued January 4, 1955; or emulsions of themixed-grain type, such as described in Carroll and Hanson U.S. Patent2,592,243, issued April 8, 1952. These agents can also be used inemulsions which form latent images predominantly on the surface of thesilver halide crystal or in emulsions which form latent imagespredominantly inside the silver halide crystal, such as those describedin Davey and Knott U.S. Patent 2,592,- 250, issued April 8, 1952. I

These may also be used in emulsions intended for use in diffusiontransfer processes which utilize the undeveloped silver halide in thenonimage areas of the negative to form a positive by dissolving theundeveloped silver halide and precipitating it on a receiving layer inclose proximity to the original silver halide emulsion layer. Suchprocesses are described in Rott U.S. Patent 2,352,- 014, issued June 20,1944, and Land U.S. Patents 2,584,- 029, issued January 29, 1952;2,698,236, issued December 28, 1954, and 2,543,181, issued February 27,1951; and Yackel et al. U.S. patent application Serial No. 586,705,filed May 23, 1956. They may also be used in color transfer processeswhich utilize the diifusion transfer of an image-wise distribution ofdeveloper, coupler or dye, from a light-sensitive layer to a secondlayer, while the two layers are in close proximity to one another. Colorprocesses of this type are described in Land U.S. Patents 2,559,643,issued July 10, 1951, and 2,698,- 798, issued January 4, 1955; Land andRogers Belgian Patents 554,933 and 554,934, granted August 12, 1957;International Polaroid Belgian Patents 554,212, granted July 16, 1957,and 554,935, granted August 12, 1957; Yutzy U.S. Patent 2,756,142,granted July 24, 1956, and Whitmore and Mader U.S. patent applicationSerial No.- 734,141, filed May 9, 1958.

In the preparation of the silver halide dispersions employed forpreparing silver halide emulsions, there may be employed as thedispersing agent for the silver halide in its preparation, gelatin orsome othercolloidal material such as colloidal albumin, a cellulosederivative, or a synthetic resin, for instance, a polyvinyl compound.Some colloids which may be used are polyvinyl alcohol or a hydrolyzedpolyvinyl acetate as described in Lowe US. Patent 2,286,215, issued June16, 1942; a far hydrolyzed celulose ester such as cellulose acetatehydrolyzed to an acetyl content of 19-26% as described in US. Patent2,327,808 of Lowe and Clark, issued August 24, 1943; a Water-solubleethanolamine cellulose acetate as described in Yutzy U.S. Patent2,322,085, issued June 15, 1943; a polyacrylamide having a combinedacrylamide content of 30-60% and a specific viscosity of 0.25-1.5 or animidized polyacrylamide of like acrylamide content and viscosity asdescribed in Lowe, Minsk and Ken-. yon U.S. Patent 2,541,474, issuedFebruary 13, 1951; zein as described in Lowe U.S. Patent 2,563,791,issued August 7, 1951; a vinyl alcohol polymercontaining urethanecarboxylic acid groups of the type described in Unruh and Smith U.S.Patent 2,768,154, issued October 23, 1956; or containing cyano-acetylgroups such as the vinyl alcohol-vinyl cyanoacetate copolyrner asdescribed in Unruh, Smith and Priest U.S. Patent 2,808,331, issuedOctober 1, 1957; or a polymeric material which results from polymerizinga protein or a saturated acylated protein with a monomer having a vinylgroup as described in U.S. Patent 2,852,382, of Illingsworth, Dann andGates, issued September 16, 8.

'If desired, compatible mixtures of two or more of these colloids may beemployed for dispersing the silver halide in its preparation.Combinations of these anti fogg-ants, sensitizers, hardeners, etc., maybe used.

The organic disulfides useful in practicing our invention can be addedto the photographic emulsions prior to the final digestion, if desired.Generally, these compounds can be added from a substantially neutralsolution so that the pH of the emulsion is not disturbed. In the case ofcompounds containing free carboxylic acid groups, this means that one ormore of these carboxylic acid groups may be neutralized. However, whereit is desired to stabilize an acidic emulsion, it is obviously notnecessary that the antifoggant be added from substantially neutralsolutions. Since the disulfides of our invention can be added to theemulsions in such small quantities, it is apparent that they willgenerally have no adverse effect upon the pH of the emulsions. Many ofthe organic disulfides useful in practicing our invention can be addedto the emulsions in the form of substantially neutral aqueous solutions.If a particular disulfide does not have sufii'cient solubility in water,addition to the emulsion can be made in the form of a water-miscibleorganic solvent, such as methanol, ethanol, dioxane, pyridine, etc.

The'amount of disulfide compound added to the emulsions of our inventioncan be varied, depending upon the particular emulsion, the silver halidecontent of the emulsion, etc. In general, we have found that from about1.0 to 10.0 grams of disulfide per mole of silver halide canadvantageously be employed in our invention. One of the outstandingadvantages .of the disulfides of our invention, as compared with thedisulfides which have been previously described in the prior art, isthat they can be used in quite substantial quantities withoutintroducing serious desensitizing effects. Moreover, as indicated above,the disulfides useful in our invention advantageously have little or nosensitizing action of their own, and hence, they can be used tostabilize emulsions which have already been finished to their optimum ornearoptimum speeds. Thus, addition of our compounds to such finishedemulsions does not result in any substantial desensitizing effect, suchas might ordinarily be expected.

The following examples will serve to illustrate the useful stabilizingeifect of many of the organic disulfides useful in practicing ourinvention. A series of coatings was made on ordinary photographic filmsupport, such as cellulose acetate, of an ordinary photographichigh-speed bromiodide emulsion, to which had been added one of theorganic disulfides of our invention at the concentration shown in thefollowing table. The compounds were added from substatnially neutralsolution and comparisons were made with an identical batch of emulsionwhich contained no antifoggant compound. After coating each series ofemulsions on a cellulose acetate support, the emulsions were driedandthen exposed on an intensity scale sensitometer (Kodak Type Ib) anddeveloped for about 4 minutes at 68 F. in a developer having thefollowing composition:

Potassium bromide do.. Cold water to make 1.0 liter.

Fresh tests and incubation tests (one week at 120 F, constant relativehumidity of about or for two weeks under the same conditions) were alsorun for the same emulsion series with development under the sameconditions. The relative speed and fog for each of the series coatingswerethen measured, the speed being determined at a point about 0.3density above fog.

In the following table, the compound numbers corre-' spond to thenumbers used above for the specific disulfides. -In each coating series,the same emulsion batch was used, although difierent emulsion batcheswere used for some of the coating numbers identified in the coatingtable. Wherever a ditferent emulsion batch was used, a new controlseries was run for that batch to show the degree of improvementobtained. The results of these coating series are given in the followingtable:

sensitivity of unsensitized or unfinished emulsions.

Table I Two Addendum Fresh Test One Week Weeks Compound Inc. Test Inc.Coating No. No. (g./ Test mol. AgX) Speed Fog Speed Fog Fog It has beenpreviously suggested in the literature that certain organic disulfideshave the useful property of increasing the speed of photographic silverhalide emulsions. It is also known that certain organic disulfides canbe used in the presence of various sulfinic or selenic acids or salts tostabilize photographic silver halide emulsions. However, the amount ofdisulfide which can be employed in these combinations is evidently quitesmall. (See Mueller U.S. Patent 2,438,716, issued March 30 1948.)Contrasted with the behavior-of the disulfides described in this patent,the disulfides of our invention can be used in gram quantities in orderto increase the stability of the emulsions, without having anysubstantial effect upon the sensitivity or speed of the emulsions. Whilethe compound of our inventions can be employed in relatively largeamounts, it has been found that such well-known disulfides as cystineand certain of its derivatives cannot be employed in amounts evenapproaching those used in the present invention. This adverse eifectaccompanying the use of cystine, or a derivative thereof, without theuse of other addenda to control the adverse effect of these compounds,is illustrated in Table II below. The strong desensitizing effect ofcystine is quite evident from the data in this table, which wereobtained in the same manner as the data given in Table I above. That is,all of these data were obtained using an ordinarygelatinosilver-bromiodide emulsion.

Table 11 Two Addendum Fresh Test One Week Weeks Compound Inc. Test Inc.Coating No. N o. (g. Test mol. AgX) Speed Fog Speed Fog Fog A cystinehydantoin. B diguanyl cystine. O cystine.

The emulsions used in arriving at the data in Tables I and II above eachwere sensitized with a labile sulfur compound, such as one of the sulfurcompounds described in U.S. Patent 1,574,994, and a gold salt, such asone of the salts described in U.S. Patent 2,399,083. The data in TableII confirm the desensitizing action of cystine in emulsions which havebeen sensitized by sulfur or gold compounds. (See Mueller U.S. Patent2,438,716, column 3, line 10.) On the other hand, cystine has theunsatisfactory property of increasing the This integer of from about 1to 4.

For example, the disulfides of Formula I can be obtained by simpleacylation of the corresponding aminodisulfides represented by thefollowing general formula:

wherein R and n each have the values given above. Acylation of thedepicted amines can be accomplished by simply reacting these amines withan acylhalide, such as acetylchloride, methanesulfonylchloride,benzenesulfonylchloride, etc. The amines of Formula II above can beprepared by simple oxidation of the corresponding mercapto-substitutedamines, represented by the following general formula:

(III) NH2 C H H2) n-SH wherein R and n each have the values given above.Oxidation can conveniently be accomplished by simply contacting themercapto-amine of Formula III with an oxidizing agent, such as hydrogenperoxide, sodium perchlorate, etc.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

What we claim as our invention and desire secured by Letters Patent ofthe United States is:

1. A photographic silver halide emulsion stabilized with from 1.0 to10.0 g./mol. of silver halide of a compound selected from the classrepresented by the following general formula:

R-NHOH(CH2)-S-S-(OH:)nONHHR C0OR 000R1 wherein R represents an acylgroup of an organic acid selected from the class consisting of analiphatic carboxylic acid, an aromatic carboxylic acid, an aliphaticsulfonic acid and an aromatic sulfonic acid, R representsa memberselected from the class consisting of a hydrogen atom, an alkali metalatom, an ammonium group, and an alkyl group, and n represents a positive2. A photographic silver halide emulsion stabilized with from 1.0 to10.0 g./mol. of silver halide of a compound selected from thoserepresented by the following general formula:

n-mromom),.ss(oHi)noHNH-R oooRl 000R1 wherein R represents an acyl groupof a carboxylic acid, R represents a hydrogen atom and n represents apositive integer of from about 1 to 4.

3. A photographic silver halide emulsion stabilized with from 1.0 to10.0 g./mol. of silver halide of a compound selected from thoserepresented by the following general formula:

R-NH o H(CH2) ..-s-s-(oH) nCHNH-R COORI COORl wherein R represents anacyl group of a sulfonic acid, R

represents a hydrogen atom and n represents a positive integer of fromabout 1 to 4.

4. A photographic silver halide emulsion stabilized with from 1.0 to10.0 g./mol. of silver halide of a compound selected from thoserepresented by the following general formula:

R-NH O H(O Ha) n--S-S(O Hz) n0 HNH-R C O 0 R1 C O 0 R1 wherein Rrepresents an acyl group of a carboxylic acid, R represents an alkylgroup and n represents a positive integer of from 1 to 4.

5. A photographic silver halide emulsion stabilized with from 1.0 to10.0 g./mol. of silver halide of a compound selected from thoserepresented by the following general formula:

OOORi COOR1 wherein R represents an acyl group of a sulfonic acid, Rrepresents an alkyl group and n represents a positive integer of from 1to 4.

6. A photographic silver halide emulsion sensitized with a labile sulfurcompound and a gold compound, said silver halide emulsion beingstabilized With from 1.0 to 10.0 g./mol. of silver halide of a compoundselected from those represented by the following general formula:

wherein R represents an acyl group of an organic acid selected from theclass consisting of an aliphatic carboxylic acid, an aromatic carboxylicacid, an aliphatic sulfonic acid and an aromatic sulfonic acid, Rrepresents a member selected from the class consisting of a hydrogenatom, an alkali metal atom, an ammonium group and an alkyl group, and nrepresents a positive integer of from about 1 to 4. Y

7. A photographic silver halide emulsion stabilize with from 1.0 to 10.0g./mol. of silver halide of the compound represented by the followingformula:

8. A photographic silver halide emulsion stabilized with from 1.0 to10.0 g./mol. of silver halide of the compound represented by thefollowing formula:

9. A photographic silver halide emulsion stabilized with from 1.0 to10.0 g./mol. of silver halide of the compound represented by thefollowing formula:

- l COOCzHs OOOCzHs A photographic silver halide emulsion stabilizedwith from 1.0 to 10.0 g./mol. of silver halide of the compoundrepresented by the following formula:

0 ll o tmoqvnono nhs-s-onionNn-ii 0 on,

0 OH 0 OH 11. A photographic silver halide emulsion stabilized with from1.0 to 10.0 g./mol. of silver halide of the compound represented by thefollowing formula:

Mueller Mar. 30, 1948 Yutzy et al. May 27, 1952 UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent N0 3 O43 696 July 10, 1962Arthur H. Herz et al.

in the above numbered pat- It is hereby certified that error appearsters Patent should read as ent requiring correction and that the saidLet corrected below.

Column 9, claim 1, and column 10, formula, each occurrence, shouldappear a of as in the patent:

claims 5 and 6, the

s shown below instead R-NHCH(CH SS(CH (\IHNH-R COOR CQOR Signed andsealed this 20th day of November 1962.

(SEAL) Attest:

DAVID L. LADD ERNEST W. SWIDER Attesting Officer Commissioner of Patents

6. A PHOTOGRAPHIC SILVER HALIDE EMULSION SENSITIVE WITH A LABILE SULFURCOMPOUND AND A GOLD COMPOUND SAID SILVER HALIDE EMULSION BEING STABLIZEDWITH FROM 1.0 TO 10.0 G./MOL. OF SILVER HALIDE OF A COMPOUND SELECTEDFROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA: